Index: capabilities.php
===================================================================
--- capabilities.php	(revision 12551)
+++ capabilities.php	(working copy)
@@ -966,6 +966,9 @@
  * @return bool
  */
 function current_user_can( $capability ) {
+	if ( is_numeric( $capability ) )
+		_deprecated_argument( __FUNCTION__, '2.0', __('Usage of user levels by plugins and themes is deprecated. Use roles and capabilities instead.') );
+
 	$current_user = wp_get_current_user();
 
 	if ( empty( $current_user ) )
@@ -987,6 +990,9 @@
  * @return bool
  */
 function author_can( $post, $capability ) {
+	if ( is_numeric( $capability ) )
+		_deprecated_argument( __FUNCTION__, '2.0', __('Usage of user levels by plugins and themes is deprecated. Use roles and capabilities instead.') );
+
 	if ( !$post = get_post($post) )
 		return false;